code: def test_property_opacity(prop):
      opacity = 0.5
      prop.opacity = opacity
      assert prop.opacity == opacity
      with pytest.raises(ValueError):
          prop.opacity = 2
  
imports: import os
  import numpy
  import pytest
  import pyvista
label_desc: Use image node_id 11 for calling a global function with example usage: test_property_opacity(prop) without return types